What does the atomic number of an element represent? question 21 options: a. the number of protons in an atom b. the number of neutrons in an atom the mass of an atom c. the total number of protons, neutrons, and electrons in an atom d. the order in which the element was discovered

Aman tries to push a box of mass 4 kg with a force of 5 n but the box remains stationary if the coefficient of static friction is 0.45, what is the value of the maximum force of friction?

Unpolarized light of intensity i_0=750w/m^2 is incident upon two polarizers. after passing through both polarizers the intensity is i_2=280w/m^2. (a) what is the intensity of the light after it passes through the first polarizer in w/m^2? (b) write an equation for the angle between the polarizers in terms of the initial (i_0) and final (i_2) intensities. (c) find the angle between the polarizers in degrees.

Hydrogen and helium are both members of?